Trace Minerals

Chromium

Chromium is involved in glucose metabolism. Studies suggest that it may play a role in insulin action and may improve blood glucose control in patients with diabetes mellitus. Recommendations regarding requirements and supplementation remain controversial because of difficulty in assessing chromium status and because there is no clearly defined chromium deficiency syndrome. Any role for chromium in changing muscle or fat distribution, in treating obesity, or in affecting lipid metabolism remains under investigation.

Selenium

Epidemiologic data suggest an inverse relationship between selenium levels and cancer incidence. In a recent study, decreased risk of total cancer incidence (excluding skin cancers) and mortality was found for middle-aged to older adults who took 200 µg of selenium (RDA = 55 to 70 µg) daily. Further studies are needed before selenium supplementation can be recommended, because high intake may cause vague gastrointestinal and skin symptoms (eg, upset stomach, fingernail changes, hair loss) and fatigue.

Zinc

Zinc is needed for adequate wound healing, immunity, and a healthy appetite (RDA = 12 to 15 mg). It may also slow progression of age-related macular degeneration. Zinc deficiency is common among malnourished elderly persons, particularly among those who also have cirrhosis or diabetes mellitus or who are taking diuretics. A high-fiber diet may interfere with zinc absorption.

Deficiency is difficult to diagnose: Serum zinc levels are a poor marker of zinc nutrition, and zinc status is difficult to accurately assess. Supplementation may be useful for patients at risk of deficiency, but high doses may cause stomach upset or interfere with copper metabolism and cause anemia. Supplementation for treatment of benign, self-limited viral upper respiratory infections is controversial; studies have had conflicting conclusions.